Heat Exchanger Release and Ammonia Release
Heat Exchanger Rupture and Ammonia Release
The CSB Case Study on the incident, examines the events leading up to the rupture of the heat exchanger and the ammonia release, and the corresponding emergency response to the event. It is clear that there were many failures and opportunities to correct and prevent this incident from occurring. As they performed their investigation, they were able to identify several direct, contributing, and root causes, although they don’t specifically designate them as such. In my opinion, I will outline what each of those causes are, and explain why I believe they fit into that specific category.
First, let’s look at the probable direct causes of this incident. In my opinion the probable direct causes are the isolation of the pressure relief valve for the rupture disk replacement, and the blocking of the valve that isolates the ammonia pressure control valve from the heat exchanger. Although there was a lockout/tagout process in place based on the information in the report and my assumption, it was not completely followed. The blocking of a relief device would need to be documented and logged, and there is no information in the report that discusses this at all. This is a critical safety system and any maintenance that is to be performed on it must be done with very specific and deliberate means. Based on the information in the report, there was no evidence that the blocked relief device was ever returned to service. Another contributing factor to this was the work order process. Based on the information in the report the work order process was not always followed by operations or maintenance, and although there was a process by which signatures were to be obtained before and after work completion, there was no evidence that such signatures were obtained for this particular process. Additionally based on the information in the study, documentation for both lockout/tagout and work orders was not
The CSB Case Study on the incident, examines the events leading up to the rupture of the heat exchanger and the ammonia release, and the corresponding emergency response to the event. It is clear that there were many failures and opportunities to correct and prevent this incident from occurring. As they performed their investigation, they were able to identify several direct, contributing, and root causes, although they don’t specifically designate them as such. In my opinion, I will outline what each of those causes are, and explain why I believe they fit into that specific category.
First, let’s look at the probable direct causes of this incident. In my opinion the probable direct causes are the isolation of the pressure relief valve for the rupture disk replacement, and the blocking of the valve that isolates the ammonia pressure control valve from the heat exchanger. Although there was a lockout/tagout process in place based on the information in the report and my assumption, it was not completely followed. The blocking of a relief device would need to be documented and logged, and there is no information in the report that discusses this at all. This is a critical safety system and any maintenance that is to be performed on it must be done with very specific and deliberate means. Based on the information in the report, there was no evidence that the blocked relief device was ever returned to service. Another contributing factor to this was the work order process. Based on the information in the report the work order process was not always followed by operations or maintenance, and although there was a process by which signatures were to be obtained before and after work completion, there was no evidence that such signatures were obtained for this particular process. Additionally based on the information in the study, documentation for both lockout/tagout and work orders was not
References: Fred A. Manuele, CSP, PE (2008), Advanced Safety Management Focusing on Z10 and Serious Injury Prevention. Hoboken, New Jersey, John Wiley & Sons, Inc. U.S. Chemical Safety and Hazard Investigation Board. (January 2011). Goodyear Houston Case Study